Hydraulically operated tools



AIDDISQN ETAL HYDHAULI CALLY OPERATED TOOLS 3 heets-Sheet 1 Filed April22, 1966 Q NR K W% Oct. 8, 1968 E. ADDISON ETAL HYDRAULICALLY OPERATEDTOOLS 3 heets-$heet 2 Filed April 22, 1966 Oct. 8, 1968 E. ADDiSON ETAL.3,404,603

HYDRAULICALLY OPERATED TOOLS Filed April 22, 1966 3 Sheets-Sheet 3United g States Patent 3,404,603 HYDRAULICALLY OPERATED TOOLS EdwardAddison and John Peter Jackson, Weymouth, Dorset, England, assignors toVickers Limited, London,

England, .a British company 1 Filed Apr. 22, 1966, Ser. No. 544,598Claims priority, application Great Britain, Apr. 23, 1965, p 17,350/ 65Claims. (Cl. 91-5) .A hydraulically operated reciprocating tool whosefluid supply is external. A double acting piston imparts repeated blowson a tool head and each forward stroke is assisted by. a hydraulicspring fitted on the tool, while the fluid forced from the exhaust sideof the piston during this stroke is ducted through the tool to reduceback pressure effects onthe piston rod. The return stroke is slowersince the hydraulic spring is then being energized by the returningpiston. The valve means for directing the fluid supply preferablyconsists of a ported cylinder, also reciprocable, in which the pistonslides.

i This invention relates to hydraulically operated tools.

According to the present invention there is provided a hydraulicallyoperated tool comprising a body; a double acting piston and cylinderassembly in the body; means for imparting, when the piston and cylinderare relatively reciprocated, motion to a tool head for engaging the workon which the tool is to operate; an inlet for connection to a source offluid under pressure, there being ducting in the body from said inlet tothe piston and cylinder assembly; valve means co-operating with theducting operable alternately to connect, in use of the tool, the inletwith one and the other of the variable volume chambers of the piston andcylinder assembly to produce a forward stroke and a return strokerespectively of the piston; and a hydraulic spring which operates on thesame liquid as that used, fpr actuating the piston, such liquid in thespring being slightly compressed by a member, which co-operates withsaid piston, upon the return stroke of the latter, thereby storingenergy which is subsequently imparted by said members to said piston toassist its forward stroke.

For a better understanding of the present invention and to show how thesame may be carried into efl'ect, reference will now be made, by way ofexample, to the accompanying drawings, in which:

FIGURE 1 is an axial section of a hydraulic hammer with its middleportion shown in outline,

I FIGURE 1A is an axial section, to a larger scale, of the middleportion of the hammer of FIGURE 1,

FIGURE 2 is a partly sectioned side view of a tool holder forming partof the hammer of FIGURE 1, and

FIGURE 3 is a section of a hydraulic fluid accumulator incorporated inthe hammer of FIGURE 1.

In the following description the right hand end of the hammer as shownin FIGURE 1 will be referred to as the lower end and the left hand endas the upper end of the hammer.

The hammer of FIGURES 1 and 1A has a cylindrical body or casing 1 havingan axial bore 1a in which a sleeve 2 is slidably mounted. The sleeve 2has an outer surface of uniform radius but its inner surface is of asmaller radius at the central portion 2a of the sleeve than at the lowerend portion 2b and the upper end portion 2c of the sleeve. The sleeve 2therefore has a lower shoulder 2d and an upper shoulder 2e at thejunction of the portions 2a and 2b, and 2a and 2c. The ends of thesleeve. are bevelled. A double piston 3 is a close sliding fit withinthe central portion 2a of the sleeve 2 and is in 3,404,603 Patented Oct.8, 1968 the form of a cylindrical block with a shallowannular recess 4around the central portion of the block. From the lower end of thepiston 3 a rod 5 extends beyond the body 1 and is a close sliding fit inthe spigot 6a of a closure cap 6. The spigot 6a fits within the lowerend portion 2b of the sleeve 2 and an O-ring 7 in an annular groove inthe cap 6 provides a seal between the latter and the body 1. A coverplate 8 in the for-m of a disc with athickened central portion aperturedto receive the rod 5 covers the lower end of the body 1 and retains thecap 6 in position against the body 1. A gland 8a surrounding the rod 5is fitted in a recess in the lower end of the cap 6 and the thickenedcentral portion of the cover plate 8 is entered in this recess to retainthe gland therein. A chamber 9 is formed around the rod 5 between thelower end face of the piston 3, the end face of the spigot 6a and theinner surface of the sleeve 2.

From the upper end face of the piston 3 extends a rod 10 of greatercross-sectional area than the rod 5, this rod 10 being a close slidingfit within a spigot 11a of a cap 11 covering the upper end of thebody 1. The spigot 11a fits within the upper end portion 20 of thesleeve 2. A chamber 12 is formed around the rod 10 between the upper endface of the piston 3, the end face of the spigot 11a and the innersurface of the sleeve 2.

A dome 13 covers the cap 11 and has handles 13a thereon. The dome 13,the cap 11 and the body 1 are secured together by bolts 14 and a block15 is clamped by its annular flange 15a between the body 1 and the cap11, the flange 15a fitting closely within a cylindrical recess in thecap 11. A seal 16 is provided between the lower face of the flange 15aand the cap 11 and a seal 17 between the upper face of the flange 15aand the base of the dome 13. The rod 10 enters freely Within a recess inthe block 15 forming a cylindrical chamber 15b, and a hydraulic springpiston 18 having a cap 18a on its upper end extends from the upper endof the rod 10 through an axial bore in the block 15, which acts as aguide for the piston 18, into the chamber 19 formed between the dome 13and the block 15. The chamber 19 is filled with fluid at high pressure.A block 20 on the lower end of the rod 18 is trapped by a T-slot formedin the upper end of the rod 10, this slot giving a lost motionconnection between the piston 18 and the rod 10. There is clearancebetween the piston 18 and the stem of the T-slot 21 and clearancebetween the block 20 and the ends of the transverse part of the T-slot21. The slot 21 is connected via an axial passage 22 in the rod 10 andradial passages 23 in the piston 3 wit-h the annular recess 4. Thepiston 18 has radial passages 24 at a point intermediate its lengthwhich meet in an axial passage 25 which extends to the upper end of thepiston 18 through the cap 18a to open into the chamber 19. At the summitof the dome opposite the upper end of the rod 18 there is provided avent plug 26. An inclined pasage 27 in the base of the dome leads fromthe chamber 19 to a non-return valve 28 housed in the flange 15a of theblock 15. The valve 28 is biased by a spring 29 to seat against theupper end of an aperture 30 through the flange 15a, the lower end of theaperture 30 opening into a radially extending recess in the base of theblock 15.

A socket 31 for a pressure supply line (not shown) is provided on thelower end of the body 1. At the base of this socket is a chamber 32 inwhich is disposed a valve poppet 33 urged by a spring 34 against a valveseat 35. A rod 36 for shifting the puppet 33 is guided in a bore,parallel to the axis of the hammer, formed through the body 1, the cap11, the flange 15a and the base of the dome 13, and is operable by meansof a lever 37 pivoted on one of thehandles 13a. The valve seat 35 is atthe lower end of a cylindrical chamber 38 Whose axis is parallel to theaxis of the hammer. The lower end of the rod 36 passes through thischamber 38, which has a closed upper end. Co-axially arranged withinthis chamber 38 is a perforated tube 39 spaced from the cylindrical wallof the chamber 38. The tube 39 is located by a recesss 40 formed in thebody 1 at the upper end of the chamber 38. A cylindrical gauze filter 41lines the inner surface of the tube 39, the gauze extending over theperforations in that tube.

A duct 42 leads from the upper end of the chamber 38 to an annulargroove 43 formed in the bore 1a of the body 1 which receives the sleeve2. A duct 44 leads from near the bottom of the chamber 38 to anotherannular groove 45 formed in the bore 1a. Between the grooves 43 and 45two further grooves 46 and 47 are formed in the bore 1a. These groovesare shallower than the grooves 43 and 45, the groove 46 being connectedby a duct 48 with an annular chamber 49 between the lower end of thebody 1 and the cap 6, and the groove 47 being connected by a duct 50with an annular chamber 51 formed between the upper end of the body 1and the cap 11. The chamber 49 can receive the lower end portion 2b ofthe sleeve 2 and the chamber 51 can receive the upper end portion 20 ofthe sleeve 2. An annular groove 52 of similar size to the grooves 43 and45 is formed in the bore 1a between the groove 45 and the chamber 49. Asimilar groove 53 is formed between the groove 43 and the chamber 51.Both grooves 52 and 53 are connected to an exhaust duct 54 extendingparallel to the axis of the hammer and open at its upper end to therecess c and via that recess to the chamber 15b. The grooves formed inthe bore 1a of the body 1 are symmetrically arranged either side of theplane midway between the grooves 46 and 47. An exhaust or return linesocket 55 in the exterior of the body 1 communicates with the duct 54and a passage 56 through the body 1 and the cap 6 places an annulargroove 6b in the inner cylindrical surface of the cap -6 incommunication with the exhaust duct 54 and thus the exhaust line socket55.

A tube 57 having a flange 57a is secured to the underside of the plate 8by bolts 58 passed through the flange 57a and through the plate 8 toengage in the body 1. This tube 57 houses a hammer head 59 attached tothe lower end of the piston rod 5. The lower end of the rod 5 is formedwith an annular notch 60 around which is engaged a split collar 61. Acylindrical collar 62 retains the collar 61 on the rod end and aretainer ring 63 is screwed into a recess in th upper end of the hammerhead with clearance between the ring and the rod 5 and between the ringand the curved outer surface of the collar 62. The ring 63 is locked tothe hammer head 59 by a grub screw 63a. This arrangement permits slightfreedom of radial movement between the hammer head 59 and the rod 5whilst securing the head 59 against any axial movement relative to therod 5.

A cover 64 is welded over the lower end of the tube 57 and a tool headholder or guide 65 is resiliently mounted below the cover 64. A toolhead 66 is permitted limited axial mvement within this holder 65, theupper end of the tool head extending through the cover 64 and through abuffer plate 67 mounted on a rubber ring on the upper side of the cover64. Studs 69 extending downwardly from the cover 64 through a flange atthe upper end of the holder 65 each have a disc 70 retained by a nut 71on the lower end thereof. Springs 72 acting between each flange andassociated disc urge the holder against the cover 64. The holder 65 haslugs 73 between which is pivoted a safety catch 74. The catch 74 is inthe form of a bell-crank lever mounted on a pivot pin 75. The longerarmof the lever normally extends upwardly along the side of the holder65 and the shorter arm extends inwardly to engage the tool head 66 at alocation below a collar 664: formed thereon. It is the collar 66aengaging the holder 65 and the catch 74 that limits the movement of thetool head relative to the body 1. A cylindrical recess 76 is provided inthe holder '65 and a plunger 77 entered in the recess 76 is urged by aspring 78 against the base I w J j: of the shorter arm of the catch 74to maintain the catch engaged with the tool head 66. The catch 74 can beturned in an anti-clockwise direction (FIGURE 2) against the action ofthe spring 78 to release the tool head 66.

The sleeve 2 has porting for co-operating with the grooves in the bore1a of the valve body 1. At the upper end of the portion 2a of the sleeve2, adjacent the shoulder 2e, ports 79, through the sleeve are spacedaround the sleeve 2, each port 79 having a width, measured. in the axialdirection of the sleeve, that is half the width of the grooves 43 or53'. At the lower end of the portion 2a, adjacent the shoulder 2d, thereis another similar set of ports 80 which have a widthhalf that of thegrooves 45 or 52. The lands between the grooves 43 and 53 and betweenthe grooves 45 and 52 each have an axial extent equal to the widthmeasured in the axial direction of the sleeve of the ports 79 and 80.Between the ports 79 and 80 on the outer surface of the portion 2a areformed annular grooves 81 and 82, these grooves having the same width asthe grooves 46 and 47. Ports 83 at the lower end of the groove 81 placethat groove in communication with the inside of the sleeve 2. Ports 84at the upper end of the groove 82 place that groove also incommunication with the inside of the sleeve 2. The grooves 81 and 82 arespaced apart by an amount equal to the spacing between the grooves 46and 47 and the ports 79 and 80 are symmetrically disposed either side ofthe grooves 81 and 82, the centre to centre spacing betweencorresponding ports 79 and 80 being equal to the centre of centre axialspacing of the grooves 43 and 52 and that between the grooves 53 and 45.

The accumulator shown in FIGURE 3 is for attenuating pressure pulses inthe supply line of hydraulic fluid to the hammer. This accumulator isarranged between the chamber 38, which in use of the hammer has highpressure fluid therein, and the exhaust duct 54. A passage 85 leads fromthe chamber 38 and has at its end remote from the chamber 38 a widerportion in which a piston 86 is a close sliding fit. Between the passage85 and the exhaust duct 54 is a cylindrical chamber 87 in which thepiston rod 88 of the piston 86 is co-axially arranged, its end remotefrom the piston 86 being slidably entered in a recess in a plug 89 whichcloses the chamber 87. A pile of spring dished washers 90 surroundingthe rod 88 are arranged with adjacent washers convex in oppositedirections to form a spring assembly which acts between the piston 86and the plug 89, urging the piston 86 into the wider portion of thepassage 85. The chamber 87 opens into the exhaust duct 54 through a port91. Any excess pressure in the chamber 38 is absorbed by movement of thepiston 86 against the resistance of the pile of spring washers 90.

For use of the hammer, a tool head 66 for engaging the work on which thehammer is to operate is mounted in the holder 65 and held there by thesafety catch 74. A pressure supply line is connected to the socket 31 by(for example) a self-sealing coupling and an exhaust return line isconnected to the socket 55.

There will now be described a complete cycle of the hammer starting fromthe position shown in FIGURE 1. It will be assumed that the valve poppet33 has been shifted away from the valve seat 35 by the lever 37. Thesleeve 2 is at the limit of its downstroke and the piston 3 is at thelimit of its upsroke. Fluid in the groove 51 is at exhaust pressure, thegroove 51 being in communication with exhaust through the duct 50, thegroove 47, the ports 84, the chamber 9 and the ports 80. The chamber 12is filled with high pressure fluid which has entered the chamber 12 viathe duct 42, the annular groove 43 and the ports 79. The chamber 19 isalso filled with fluid at high pressure and the piston 20 is thereforeassisting in urging the rod 10 downwards. In practice the principalforce on the piston 3 will be from the piston 20 rather from the fluidin the chamber 12. The grooves 45 and 53 are blanked ofl? by the ut surfof the sleeve 2,.the lower end. of the piston 3 blocks the ports 83,and-fluid in the chamber 49 is at exhaust p'ressure, the chamber 49having just been cut off from exha'ust viathe recess 4, thezpassages 23and 22, the'T-slot ZLtheachamber 15b and the recess15c by the piston 3blocking the ports 83. The high pressure fluid in the chamber 12 actingon the shoulder 2e maintains the sleeve 2 against the'cap6.

With high pressure fluid in the chamber 12 and the piston 18 urgingtherod downwards, the downstroke begins. The ports 79 are immediatelycompletely opened by the piston 3 moving downwards, fluid is expelledfrom the chamber 9, and the recess 4 in the piston 3 comes into registrywith the ports 83. Some fluid from the chamber 9 escapes to the exhaustreturn line, but most of the fluid from the chamber 9 passes along theduct 54 and the recess c and into the chamber 15b which is being vacatedby the rod 10. At the same time the ports 84 are sealed off by thepiston 3 but will later also come into registry with the recess 4 as theports 83 are about to be cut-off again by the piston 3. No change takesplace in the position of the sleeve 2 since fluid at high pressure stillacts on the shoulder 2e.

Further downward movement of the piston 3 forces more fluid from thechamber 9 into the recess 15c and thence into the chamber 15b, anduncovers the ports 83 again. Fluid at inlet pressure is thereforeadmitted via the duct 48 to the chamber 49, and this high pressurefluid, by virtue of the bevelled edge of the end of the sleeve portion2b exerts an upward pressure on the sleeve 2 greater than the downwardforce on the shoulder 2e. The sleeve 2 therefore starts to move in anupward direction, opposite to that of the piston 3. Oil from the chamber51 escapes via the duct 50 and the ports 84 into the recess 4 and thenceinto the passages 23 and 22.

As the piston 3 reaches the bottom of its downstroke, the sleeve 2 movesup to abut the cap 11, the ports 79 being moved away from the groove 43and coming into registry with the groove 53 so that the chamber 12 isopen to exhaust via the port 79, the groove 53 and the duct 54. Thegroove 43 is blocked by the outer surface of the sleeve 2 but the groove45 is in communication via the ports 80 with the chamber 9 and thereforehigh pressure fluid acts on the bottom end face of the piston 3 and onthe shoulder 2d at the bottom of the middle portion 2a of the sleeve 2.The sleeve 2 is therefore urged against the cap 11 and the piston 3 isstarted on its return or upstroke. At the bottom of its stroke thehammer head 59 delivers a blow on the tool head 66. Should it overrunbeyond a certain limit the head 59 is arrested by the buffer plate 67which offers a resilient resistance by virtue of its mounting on therubber ring 68. The cover 64 offers a final stop to the buffer plate 67.Also at the bottom of the stroke, the rod 10 moves so that the block isleft at the top of the transverse part of the T-slot 21 since the cap18a on the upper end of the piston 18 arrests the piston 18 before thepiston 3 bottoms.

The pressure of fluid in the chamber 9 pushes the piston 3 upwards andexhaust fluid from the chamber 12 is expelled through the ports 79, viathe groove 53 to the exhaust duct 54. The sleeve 2 remains in itsuppermost position. The bottom of the transverse part of the T-slot 21re-engages the bottom end face of the block 20 and forces the piston 18up into the chamber 19, compressing the fluid in that chamber andstoring up energy for the downstroke. The sequence of events during thereturn stroke corresponds to similar ones on the downstroke and thechange-over of the sleeve at the end of the stroke is similar to whathas already been described.

It will be understood that the downstroke is faster than the upstroke.This is because the downstroke is assisted by the pressure of fluid inthe chamber 19 acting through the piston 20, and the freer exhaustcreated by the chamber 9 partly diverted to the expanding chamber 15Brather than wholly via the passage 55. andythejfull resistance of theexhaust line. Also, on the return stroke, the piston 3 has to workagainst the action of the fluid under pressure in the chamber19,.andthepiston-rod 10 has to do work in expelling fluid from therecess 15b. The duct 54 has the effect of evening out the flowrpulses inthe exhaust line.

Should the pressure difference between the fluid in the exhaust-duct 54and in the chamber19fall'below a certain value, the non-return valve 28will open 'the aperture 30 so that any loss. of oil from the chamber 19is made up. Fluid-that might leak from the chamber 19 along the rod 5between the latter and the.spigot .6u of the cap 6 will be vented viathe groove 6b and the passage 56 to exhaust. Any fluid that passesbeyond the groove 61: is prevented from escaping by the gland8a.

Fluid in the chamber 19 is compressed slowly on the upstroke of thepiston 18 as compared with the decompression that takes place when thepiston 18 is on the downstroke. Oil on the piston 18 in the closeclearance fit in the block 15 leaks or is wiped off at dilferent ratesand this might cause a possible pumping action in which oil would beinjected from the chamber 15b into the chamber 19, building up thepressure of fluid in that chamber. This would have the undesirableeffect of making the spring effect of the piston 18 stiffer. Thepassages 25 and 24 allow excess pressure fluid in the chamber 19 toescape into the chamber 15b at the bottom of the hammer stroke.

The fluid used in the above described hammers will have a certaincompressibility to permit movement of the piston 18. A normal mineraloil having a compressibility such that the volume change is /2 per 1,000p.s.i. has been found suitable. For example with a W in. diam eterpiston (.249 in. area) having a 2 in. stroke in a 25 cubic inch chamber19, the .498 in. compression gives a peak pressure of 3,990 psi. and astiffness of 496 lbs./ inch.

The porting in the sleeve 2 has been described as symmetrical. In orderto assist the difference in speed in downward and return stroke theporting could be modified to make the arrangement asymmetrical or thepiston 3 could have its upper end face cut back so that on the downstroke the ports 83 would be uncovered earlier to cause an earlier shiftof the sleeve 2.

What is claimed is:

1. A hydraulically operated tool comprising (a) a body with ductingtherein for hydraulic fluid and with an inlet and outlet for connectionto an external fluid supply.

(b) a double acting piston and cylinder assembly in the body and havinga first variable volume chamber for pressure fluid supplied thereto tocause a forward stroke and a second variable volume chamber for pressurefluid supplied thereto to cause a return stroke.

(c) a tool head for engaging the work on which the tool is to operate,

(d) means for imparting motion to the tool head when the piston andcylinder are relatively reciprocated,

(e) valve means co-operating with said ducting for alternatelyconnecting said first and second chambers to said inlet via saidducting,

(f) a hydraulic spring mounted on said body and operative on saidhydraulic fluid,

(g) a member connecting said spring with the piston of said assembly tourge the latter in the direction of said forward stroke and to storeenergy by compressing the fluid in said spring on said return stroke,

(h) a third chamber is said body between said first chamber and saidhydraulic spring into which said connecting member extends and intowhich a piston rod of the piston and cylinder assembly extends, theconnecting member and said piston rod being coupled in said thirdchamber, and

(i) further ducting in said body between said third chamber and saidsecond chamber and connected to said outlet, closed by said valve meanson the return stroke for fluid in said third chamber to escape to saidoutlet and opened by said valve means on the forward stroke to passfluid from said second to said third chamber.

2. A tool according to claim 1, wherein the means for coupling saidconnecting member and said piston rod in said third chamber is a lostmotion connection.

-3. A tool according to claim 1, including a one-Way valve in said bodybetween said further ducting and said hydraulic spring for passage offluid from said further ducting to said hydraulic spring at and below apredetermined pressure differential therebetween.

4. A tool according to claim 1, wherein said connecting member has apassage therethrough, one end opening into the fluid chamber of saidhydraulic spring and the other opening into said third chamber at theend of said forward stroke, said passage being otherwiseclosed by saidbody.

5. A tool according to claim 1, wherein the cylinder of the piston andcylinder'assembly. is a sleeve reciprocably mounted in a tool body withporting therein forming said valve means. I a 1 References Cited UNITEDSTATES PATENTS 3,088,440 5/1963 Wilmer 91 -5 3,150,488 9/1964 Haley60-51 3,183,668 5/1965 Johnson 6051 3,186,169 6/1965 Hauser 91 53,213,615 10/1965 Bjornberg 60-51 MARTIN P. SCHWADRON, Primary Examiner.

B. L. ADAMS, Assistant Examiner.

